Chapman David, Barnett Rob, Yartsev Slav
London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.
London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.
Med Dosim. 2014 Summer;39(2):159-62. doi: 10.1016/j.meddos.2013.12.002. Epub 2014 Jan 13.
To design a quality assurance (QA) procedure for helical tomotherapy that measures multiple beam parameters with 1 delivery and uses a rotating gantry to simulate treatment conditions. The customized QA procedure was preprogrammed on the tomotherapy operator station. The dosimetry measurements were performed using an ArcCHECK diode array and an A1SL ion chamber inserted in the central holder. The ArcCHECK was positioned 10cm above the isocenter so that the 21-cm diameter detector array could measure the 40-cm wide tomotherapy beam. During the implementation of the new QA procedure, separate comparative measurements were made using ion chambers in both liquid and solid water, the tomotherapy onboard detector array, and a MapCHECK diode array for a period of 10 weeks. There was good agreement (within 1.3%) for the beam output and cone ratio obtained with the new procedure and the routine QA measurements. The measured beam energy was comparable (0.3%) to solid water measurement during the 10-week evaluation period, excluding 2 of the 10 measurements with unusually high background. The symmetry reading was similarly compromised for those 2 weeks, and on the other weeks, it deviated from the solid water reading by ~2.5%. The ArcCHECK phantom presents a suitable alternative for performing helical tomotherapy QA, provided the background is collected properly. The proposed weekly procedure using ArcCHECK and water phantom makes the QA process more efficient.
设计一种用于螺旋断层放射治疗的质量保证(QA)程序,该程序通过一次照射测量多个射束参数,并使用旋转机架模拟治疗条件。定制的QA程序在断层放射治疗操作员工作站上预先编程。剂量测量使用插入中央支架的ArcCHECK二极管阵列和A1SL电离室进行。ArcCHECK位于等中心上方10厘米处,以便21厘米直径的探测器阵列能够测量40厘米宽的断层放射治疗射束。在实施新的QA程序期间,在10周的时间内,分别使用液体水和固体水中的电离室、断层放射治疗机载探测器阵列以及MapCHECK二极管阵列进行了对比测量。新程序获得的射束输出和剂量率与常规QA测量结果具有良好的一致性(在1.3%以内)。在10周的评估期内,测量的射束能量与固体水测量结果相当(0.3%),不包括10次测量中有2次背景异常高的情况。这两周的对称性读数同样受到影响,在其他周,它与固体水读数的偏差约为2.5%。如果背景采集得当,ArcCHECK模体是进行螺旋断层放射治疗QA的合适替代方案。所提出的使用ArcCHECK和水体模的每周程序使QA过程更加高效。